AFO devices are designed to correct gait impairments for patients by stabilizing and securing the ankle-foot complex during gait. AFOs can be required for patients affected by a wide range of conditions including direct injury to the dorsiflexors, the common peroneal, the sciatic nerves, or the neural pathways that supply them. AFOs are also used to treat gait impairments resulting from conditions such as cerebral palsy, multiple sclerosis, or scoliosis, and are also common among subjects post-stroke who cannot properly dorsiflex their ankle or extend their toes.
The process of fitting an AFO to a patient is typically done by a skilled clinician who selects an AFO based on the patient's condition, the patient's foot/shoe size, the patient's activity level and/or the patient's weight. If appropriate, the patient is fitted with a standard, off-the-shelf (“OTS”) AFO. However, for patients with deformities or gait irregularities, a custom AFO is often necessary.
Once fitted, the AFO is often placed into the patient's shoe, underneath an insole. The insole can be a standard, unmodified insole or it can provide some corrective support, as needed.
Many known AFOs, both OTS and custom, concentrate on the ankle and knee biomechanics while aligning the patient's foot parallel to the patient's longitudinal axis or straight ahead from back to front. For instance, known AFOs align the user's foot straight ahead during gait. Most people however do not walk with their feet pointed straight ahead. Rather, most people walk with their feet externally rotated. Thus, conventional AFOs are known to resist typical foot rotation during gait. This can be problematic and even detrimental to a patient, adding stress and causing coronal plane or torsional loading on the knee as well as instability and discomfort.
Such unnatural foot motion can also cause foot and leg fatigue because it conflicts with normal gait of a patient, requiring the wearer to adjust or correct the position of the wearer's foot while ambulating. It also can create awkward pressure points on the patient's lower leg and/or foot as a result of the AFO being urged unnaturally against the wearer's lower leg and/or foot while ambulating.
Many known AFOs also flex in such a way that they impinge upon the wearer's heel, which in turn, can cause discomfort at the distal attachment of the Achilles tendon or other problems during use.
In addition to resisting typical foot rotation during gait, existing AFO designs that incorporate posterior struts do not easily allow for adaptations for anterior components, using only fabric straps wrapped around the anterior aspect of the calf. However, as gait motion is forwardly (anterior), a rigid posterior strut with a flexible anterior element can be counter-productive and can lead to complications during gait where a patient tends to lean back in the AFO, negatively impacting balance and stability. Furthermore, fabric straps secured too tightly can lead to lines of pressure from the straps resulting in discomfort and, in extreme cases, reduction in blood flow to the limb.
Existing AFO designs that incorporate either medial or lateral struts that transition to an anterior component often have the limitation of transferring force from the calf, which is normal to the anterior shell, into the medial or lateral strut, which is 90 degrees from the anterior shell, to a footplate, providing counterforce from the ground, which is again 90 degrees from the strut. This often results in force transfer between the different elements being not only not normal to the gait motion, but also at disadvantageous angles, resulting in gait inefficiency as well as a tendency to fail prematurely. It may also feel counter-intuitive or unnatural for new users, who are unfamiliar with the typical feeling of these products.
Furthermore, OTS AFO designs are not adjustable and cannot accommodate a large range of users, while custom AFO designs are time-consuming and expensive to produce.
There is Thus a Need for an Orthotic System that is More Comfortable, Versatile, and Encourages More Natural Biomechanics of the Foot, Ankle, and Lower Leg.